Proteins are critically important to life and the human
body. They are also among the most complex molecules in nature,
and there is much we still don’t know or understand about
them.

One key challenge is the stability of enzymes, a particular
type of protein that speeds up, or catalyzes, chemical
reactions. Taken out of their natural environment in the cell
or body, enzymes can quickly lose their shape and denature.
Everyday examples of enzymes denaturing include milk going
sour, or eggs turning solid when boiled.

Rensselaer Polytechnic Institute Professor Marc-Olivier Coppens has
developed a new technique for boosting the stability of
enzymes, making them useful under a much broader range of
conditions. Coppens confined lysozyme and other enzymes inside
carefully engineered nanoscale holes, or nanopores. Instead of
denaturing, these embedded enzymes mostly retained their 3-D
structure and exhibited a significant increase in activity.

“Normally, when you put an enzyme on a surface, its activity
goes down. But in this study, we discovered that when we put
enzymes in nanopores — a highly controlled environment — the
enzymatic activity goes up dramatically,” said Coppens, a
professor in the Department of Chemical and
Biological Engineering at Rensselaer. “The enzymatic
activity turns out to be very dependent on the local
environment. This is very exciting.”

Results of the study are detailed in the paper, “Effects of
surface curvature and surface chemistry on the structure and
activity of proteins adsorbed in nanopores,” published last
month by the journal Physical Chemistry Chemical
Physics. The paper may be viewed online at: http://dx.doi.org/10.1039/C0CP02273J

Researchers at Rensselaer and elsewhere have made important
discoveries by wrapping enzymes and other proteins around
nanomaterials. While this immobilizes the enzyme and often
results in high stability and novel properties, the enzyme’s
activity decreases as it loses its natural 3-D structure.

Coppens took a different approach, and inserted enzymes
inside nanopores. Measuring only 3-4 nanometers (nm) in size,
the enzyme lysozyme fits snugly into a nanoporous material with
well-controlled pore size between 5 nm and 12 nm. Confined to
this compact space, the enzymes have a much harder time
unfolding or wiggling around, Coppens said.

The discovery raises many questions and opens up entirely
new possibilities related to biology, chemistry, medicine, and
nanoengineering, Coppens said. He envisions this technology
could be adapted to better control nanoscale environments, as
well as increase the activity and selectivity of different
enzymes. Looking forward, Coppens and colleagues will employ
molecular simulations, multiscale modeling methods, and
physical experiments to better understand the fundamental
mechanics of confining enzymes inside nanopores.

The study was co-authored by Lung-Ching Sang, a former
Rensselaer graduate student in the Department of Chemical and
Biological Engineering.